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  • drill jig setup

    What is the correct (preferred) way to align a drill bit or milling cutter with holes in a drilling jig? For example, should the jig be first clamped to the milling table and then move the x-y table axis until it “feels like” the drill is entering the hole without interference or should you place the drill into the hole and carefully lower the quill and jig to the table and then clamp the jig to the table before raising the quill?

    Second part of this question, "If the jig is fabricated from aluminum (Class 3 anodized surface), what is the best way to protect the holes in the jig thus preserving accuracy for repeated use"?

    Harold
    For those having fought for it, Freedom has a flavor the protected will never know.
    Freedom is only one generation away from extinction.

  • #2
    Proper way:
    Use a spinning center finder and touch the inside of the hole at four points.

    Less proper way:
    Use a non-spinning center finder and poke it into the hole with the quill. Feel the offset of the center finder with your fingernails and move the xy table until the offset goes away. Then rotate the spindle half a turn and repeat, in case there is any runout on the center finder.

    Lazy way:
    Make sure the drill is not bent. Place your finger against the drill with the lightest possible pressure. Use the quill to poke the drill into the hole and feel if there is any deflection. Then rotate the spindle half a turn and repeat.

    No idea on part 2.

    Comment


    • #3
      'orses

      Part/question 2.

      Insert (press) a hardened steel sleeve/bush - or at a pinch - unhardened steel.

      Pressing in is easiest but making the bush removable/replaceable is better.

      What-ever suits - horses for courses.

      Comment


      • #4
        beanbag, pardon my ignorance but please explain the first method with the center finder. I have a center finder set but the only tip I've ever used is the pointy one. Does this method use one of the other tips?

        I've always used my Last Word (last chance?) to find hole centers if I needed accuracy. I think I can get within .0005" with it. If there is another method to do it I'd like to know.

        Comment


        • #5
          My take on part 2, If the jig is to be for many uses then make hardened inserts to fit these can then be changed if they get 'too loose' as per dowelling jigs. Inserts can have flange at top with flat so screwin jig plate stops it rotating.
          My 2p worth.
          On the first I've always centered on the drill then clamped the jig to the table, usually good enough for my level of accuraccy thats why I use ajig.

          Peter
          I have tools I don't know how to use!!

          Comment


          • #6
            Originally posted by oldtiffie
            Part/question 2.

            Insert (press) a hardened steel sleeve/bush - or at a pinch - unhardened steel.

            Pressing in is easiest but making the bush removable/replaceable is better.

            What-ever suits - horses for courses.
            Good morning Tiffie,

            I have most likely missed something here, or because of brevity I failed to provide sufficient information. Please allow me to provide more information.

            I have purchased a rather expensive aluminum jig. This jig has 9 precisely placed holes of varying sizes that are to be used as guides when when drilling into the work piece. I am fearful that the flutes of the drill bits with score, erode, or otherwise alter the guidance holes with use. I think I am hearing you say that I should enlarge the holes of the jig and fabricate hardened steel bushings that can be press fitted into the jig. There are places on the jig with sufficient space which would allow for this but several of the holes are *very* close to each other while two holes are against edges at either end.

            Should I expect, that if careful, I will be able to reuse this jig 5 or 6 times before hole distortion occurs due to drill flutes eating away at the sides of the jig holes? I have heard that Class 3 anodized aluminum can be quite hard but I have no idea how much protection this offers.


            Harold
            For those having fought for it, Freedom has a flavor the protected will never know.
            Freedom is only one generation away from extinction.

            Comment


            • #7
              This is DEFINITLEY an amature's suggestion. First, I assume that this jig is not intended for hundreds of uses. Why not buy a drill blank of the size of the drill you are using? Chuck the blank and use it to align the jig and clamp it down. Then instal a drill and have at it.
              Duffy, Gatineau, Quebec

              Comment


              • #8
                Originally posted by ptjw7uk
                My take on part 2, If the jig is to be for many uses then make hardened inserts to fit these can then be changed if they get 'too loose' as per dowelling jigs. Inserts can have flange at top with flat so screwin jig plate stops it rotating.
                My 2p worth.
                On the first I've always centered on the drill then clamped the jig to the table, usually good enough for my level of accuraccy thats why I use ajig.

                Peter
                Good Morning Peter,

                I appreciate your 2p worth of suggestions. One slight inaccuracy is often a multiplying factor causing all sorts of "head scratching conundrums" as one approaches the end of a project. Naturally, I would LOVE to minumize "problem solving" and "last minute modifications". To this end I seek to be as accurate as my machines and instruments will allow.

                Harold
                For those having fought for it, Freedom has a flavor the protected will never know.
                Freedom is only one generation away from extinction.

                Comment


                • #9
                  Originally posted by Duffy
                  This is DEFINITLEY an amature's suggestion. First, I assume that this jig is not intended for hundreds of uses. Why not buy a drill blank of the size of the drill you are using? Chuck the blank and use it to align the jig and clamp it down. Then instal a drill and have at it.
                  I have thought of that and have already ordered drill blanks for use. Unless others have a better way, I think this might be the best alternative.

                  Thanks for reaffirming my thought process. Make me feel better about my planning.

                  Harold
                  For those having fought for it, Freedom has a flavor the protected will never know.
                  Freedom is only one generation away from extinction.

                  Comment


                  • #10
                    You could grind a point on the drill blanks making them into transfer punches. I have several aluminum drill fixtures I use with punches and with drill bits. Hard bushings are pressed into the fixture and then it's clamped to the part. Sometimes I even use a hand drill to make the holes. The drill bushings were replaced a couple of times in ten years. I've made thousands of parts with this setup.

                    Comment


                    • #11
                      Secure the part/fixture and use a DTI and sweep the bore to align the spindle over it.

                      Comment


                      • #12
                        Hasten slowly

                        Originally posted by hwingo
                        Good morning Tiffie,

                        I have most likely missed something here, or because of brevity I failed to provide sufficient information. Please allow me to provide more information.

                        I have purchased a rather expensive aluminum jig. This jig has 9 precisely placed holes of varying sizes that are to be used as guides when when drilling into the work piece. I am fearful that the flutes of the drill bits with score, erode, or otherwise alter the guidance holes with use. I think I am hearing you say that I should enlarge the holes of the jig and fabricate hardened steel bushings that can be press fitted into the jig. There are places on the jig with sufficient space which would allow for this but several of the holes are *very* close to each other while two holes are against edges at either end.

                        Should I expect, that if careful, I will be able to reuse this jig 5 or 6 times before hole distortion occurs due to drill flutes eating away at the sides of the jig holes? I have heard that Class 3 anodized aluminum can be quite hard but I have no idea how much protection this offers.


                        Harold
                        Harold.

                        As the holes are so close to each other, I'd offer two solutions which can be used either separately or in combination if needs be.

                        1.
                        Make thin-walled sleeves that fit into the existing holes. The sleeves need a hole to suit a smaller drill. Fit the sleeves and use then as guides to drill the smaller hole/s say 1/8">1/4" deep.

                        Use those holes as "pilots" for the required drills

                        2.
                        Use shortened drills such that there is as little/short spirals/flutes left. Use the now smooth(er?)-sided drills to "spot" say 1/8">1/4" deep. Use normal size drills to "finish off". The previous/ly shallower depth holes will act as "pilots".

                        Frankly, I'd drill, say 1/64">1/32" under-size and finish off with the correct sized drills for greater accuracy.

                        As the jig is aluminium and to prevent or minimise "galling" - which can not only lead to excessive wear but seizure of the drill/s in the hole/s, I'd suggest slow speeds and lots of good cutting/tapping oil. Keep all drills sharp at all times. Clear swarf continuously as it too can cause galling or seizure in aluminium.

                        A pic with a ruler for appreciation of scale will assist if possible.

                        Hasten slowly.

                        Comment


                        • #13
                          hwingo, the fact that it's made of aluminum tells me it's a one time use jig. If you run a drill through the hole to drill the part underneath the hole will be enlarged from drill wander/wobble.

                          Can you make a steel jig like the aluminum jig? If not then you can't drill through the holes and reuse the aluminum jig, it just won't last and remain accurate.

                          Make a plate to mount the part on that you can clamp to the drill press or mill. Then mount the jig on the part and use a drill blank to align a hole, clamp the plate down, remove the jig and drill the hole with a short screw machine drill or spotting drill and finished as needed. Do each hole as outlined above.

                          That is the only way you can save the jig for reuse and maintain accurate holes in the jig. Yep, it will take a lot of time but that is what it takes sometimes.
                          It's only ink and paper

                          Comment


                          • #14
                            Originally posted by strokersix
                            beanbag, pardon my ignorance but please explain the first method with the center finder. I have a center finder set but the only tip I've ever used is the pointy one. Does this method use one of the other tips?

                            I've always used my Last Word (last chance?) to find hole centers if I needed accuracy. I think I can get within .0005" with it. If there is another method to do it I'd like to know.
                            Poke the pointy end part-way down the hole, approximately near the center. Move left until it touches, then zero DRO. Then move right until it touches, and set the dro to half that value. Now you've found the center in x. Repeat for y.

                            I use this method for small holes.

                            Comment


                            • #15
                              Originally posted by hwingo
                              I am fearful that the flutes of the drill bits with score, erode, or otherwise alter the guidance holes with use.
                              If you put a little radius at the outer cutting edge of the drill, that will reduce a drill's tendency to score up your jig. It will make your drilled holes a tiny bit smaller, though.

                              Comment

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